Plastic debris as ecological drivers of green turtle microbiome and their connectivity with antibiotic resistance...

Plastic pollution in oceans threatens marine life not only through ingestion and entanglement but also as a surface for microbial colonization, harboring potential pathogens and antibiotic resistance genes (ARGs). Sea turtles, particularly green turtles (Chelonia mydas), are susceptible to plastic ingestion, making them useful sentinels of plastisphere impacts. This study investigated whether plastic-associated microbiota influence the turtle microbiome and act as vectors for potential pathogens and ARGs. We compared microbial communities across turtles, plastic debris, seawater, and two algal species representing their natural diet to assess anthropogenic versus natural drivers. The microbiome was evaluated by 16S rRNA amplicon sequencing, and the resistome by high-throughput quantitative PCR targeting ARGs. Unexpectedly, the turtle microbiome was more similar to plastic-associated communities than to algae or seawater. Genera including potential pathogens, such as Vibrio, Pseudomonas, Bacillus, Staphylococcus, and Clostridium, were shared between plastics and turtles. Although ARGs were abundant across all sample types, their profiles indicated limited transfer between plastics and turtles, revealing a decoupling between microbiome and resistome connectivity. These findings suggest that potential pathogens may be more effectively transmitted from plastics to hosts than resistance determinants. Overall, plastic debris acts as an ecological driver reshaping host-associated microbiomes more strongly than natural diet or seawater, while exerting limited influence on resistome structure, functioning as an active microbial vector of opportunistic pathogens.